FIELD OF THE INVENTION
The invention relates to a method for setting the cutting register for a cross-cutting device disposed downline of a web-fed printing press.
Ordinarily, a web passes over a great distance before it reaches a cross-cutting device, after the web has left the last printing unit of a web-fed printing press. While traversing this distance, the web is subjected to the action of additional devices for the aftertreatment of a freshly printed web, such as driers or cooling devices, for example, and is speed-dependently influenced in the position thereof by transport devices, including web-tension controllers.
In the presetting of the web-fed printing press for printing, it has become known heretofore for the phase position of a cutting cylinder of a cross-cutting device to be set manually so that the cutting line lies precisely in the intended region of the web, e.g., in the vicinity of the channel or gap formed in the rubber-blanket cylinder and in the region between two consecutive printed images, respectively. The pressman proceeds in a manner wherein, when the web-fed printing press is being set up, the printed product is constantly being subjected to a visual inspection after it leaves the cross-cutting device and, simultaneously, the phase position is being set to conform to a setpoint value by means of an input device. Only after the pressman has confirmed the desired (setpoint) position of the cutting line via the input device does a control system take over an automatic feedback control or regulation of the cutting register. Provided for this purpose inside the cross-cutting device is a device for scanning the printed image, the scanning device being directed towards the web and possibly being adjustable transversely with respect to the web-transport direction. Digitized image data which are recorded by the scanning device at the instant of confirmation by the pressman serve as the setpoint values for the feedback control or regulation of the cutting register. The feed-back-regulating device, which is present in the control system, supplies signals to actuators for setting the cutting register, the phase deviation between the setpoint-image data and the actual-image data being regulated to zero or to a fixed value.
A disadvantage thereof is that, during the setting-up of the printing press, a given period of time elapses before the desired (setpoint) position of the cutting line is confirmed by the pressman, and considerable waste is produced during this period of time. Furthermore, in order to avoid producing an unnecessary quantity of waste, the desired (setpoint) position is usually determined at a low printing-press speed, as a result of which the determination of the desired (setpoint) position is faulty, because idynamic influences under production conditions require a correction to the setpoint value.
It is accordingly an object of the invention to provide a method for presetting the cutting register on a web-fed printing press wherein the set-up time of the printing press is shortened, the production of waste is reduced, and the setting accuracy is improved.